1. Field of the Invention
The present invention relates to a device for the femoral fixation of the semitendinosus and gracilis for the reconstruction of the anterior cruciate ligament (indicated at ACL hereinafter for the sake of simplicity) of the knee.
2. Background Art
At first, it was common belief that, in the reconstruction of the ACL, the patellar tendon could ensure the utmost strength, owing to its mechanical properties and to the fact that it has bone blocks at both the ends. Then, evidence was provided that both the semitendinosus (indicated at ST hereinafter for the sake of simplicity) and gracilis (indicated at G hereinafter) tendons have mechanical properties which are comparable to, and even higher than, those of the patellar tendon.
However, it has to be noticed that, when compared to patellar tendon, doubled ST and G tendons have worse properties as far as the fixation to the bone is concerned, due to the absence of bone blocks at its ends. Namely, it was demonstrated that a defective primary fixation of doubled ST and G is more frequently affected by postoperative laxity.
Therefore, various femoral or tibial fixation techniques were proposed, with the object of achieving the firmest possible connection to the bone. The related surgery procedures usually involve an auxiliary lateral incision at the level of the lateral femoral metaphysis, a number of steps which can make the operation longer, and possible problems in the graft insertion step. Consequently, such procedures require a prolonged learning curve for the surgeon.
Presently the operation is carried out by forming two bone tunnels, one in the tibia and one in the femur. The tibial tunnel is drilled first, aiming at the centre of the anatomic ACL insertion area into the joint, using cannulated reamers and a K-wire as a guide. The harvesting of the ST and G tendons is made using a commercially available stripper, which strips the tendons well beyond the musculotendinous junction. The tendons are then freed and detached distally. After accurate cleaning and removal of all muscle remnants, the ends of the two tendons are sutured together. Namely, the ST and G tendons are looped around a mersilene tape firmly fixed to a metal bar. This kind of device is used to fix the graft to the femur. The graft quadrupled and mounted with the mersilene tape and the metal bar is inserted into the joint through the bone tunnels, firstly through the tibial and then through the femoral one. Thus, the fixation is achieved by pulling the graft and bending the metal bar over the lateral cortical surface of the femur.
The above described operation has the following remarkable drawbacks. Firstly, the fixation device, once inserted, cannot be removed unless the graft is cut. Besides, the area of the cortex against which the metal bar abuts is too narrow. Moreover, thexe2x80x94relativelyxe2x80x94substantial width of the fixation device disturbs the muscles adjacent to the abutment area on the cortex. Finally, the use of the mersilene tape results in a very low failure load and inadequate stiffness.
It is an object of the present invention to overcome the above mentioned drawbacks, providing a new device for the femoral fixation of the semi tendinosus and gracilis tendons for the reconstruction of the anterior cruciate ligament which, in particular, affords what follows:
the accomplishment of a directxe2x80x94i. e. without intermediate junctions which could represent weak bridgesxe2x80x94fixation between the graft and the lateral femoral cortex;
high failure load, comparable with that of the graft;
very high stiffness in order to obtain a rigid fixation and prevent the graft slippage;
a simple insertion, and a simple possible removal in any step of the operation;
a fixation of the graft which is very similar to the original fixation of the native ACL; and
a wide abutment area against the cortical surface, without disturbing the adjacent muscles.
According to the invention, said objects are achieved with a device for the femoral fixation of the ST and G tendons for the reconstruction of the ACL of the knee, comprising: an elongated body; means for anchoring the tendons to said body, formed in correspondence to a distal end thereof; and a set bar pivotally supported by the elongated body about a transverse axis in correspondence to a proximal end thereof. The set bar comprises a couple of coaxial stop arms and is pivotable between two insertion positions, angularly spaced by 180xc2x0, in each insertion position a respective stop arm extending beyond the proximal end of the elongated body, coaxially thereto. In this way, keeping the set bar in a insertion position, the device is inserted into consecutive tunnels preliminarily formed in the tibia and femur, until the proximal end of the body partly projects out of the femoral tunnel. In such condition, said set bar is rotated to a fixation position, intermediate between said insertion positions, in order to cause the abutment of said stop arms of the set bar against the surface of the femur. The sliding of the body within said tunnels and the rotation of the set bar are operated via threads attached to respective stop arms.